The Department of Homeland Security is looking for more than 6,000 foreign nationals who came to the U.S. on student visas and have disappeared from the U.S. government’s radar.

“My greatest concern is that they could be doing anything,” Peter Edge, the U.S. Immigration and Customs Enforcement official who oversees investigations into visa violators, told ABC News on Tuesday. “Some of them could be here to do us harm.”

Homeland Security officials disclosed to the news outlet that 58,000 students potentially overstayed their visas in the past year alone. The 6,000 who are unaccounted for spotlights a security gap that was supposed to be closed after the September 11, 2001, terrorist attacks, ABC News reported.

ICE agents attempting to find the missing students told the news outlet that in terms of creating a safe student visa program, the U.S. has “a lot more work to do.”

“We know we have a lot of nonaccredited universities that are using this system to bring people in, collect money and not educate them at all,” Republican senator Tom Coburn of Oklahoma told ABC News. “To me, it’s a mess.”

6,000 leads to its 26 Homeland Security Investigations field offices for further investigation; DHS knows where these individuals are.

The news outlet reported that there are more than 9,000 schools approved to accept foreign nationals. Included on the list are massage schools, academies for teaching tennis and beauty schools.

In an attempt to better police the system, ICE plans on hiring 60 field representatives, who will travel around the country to inspect schools that have been approved to accept foreign students, an officer with the agency told the news outlet.

Update: Katie O’Connell, Associate Director, Media Relations and Advocacy, at NAFSA: Association of International Educators, reached out to The Washington Times to contest ABC’s reporting, saying, “It is simply not true that these students are lost; they were referred to one of DHS’s 26 field offices because their location is known.” ABC has not retracted any of its reporting on the story as of Sept. 10.